The effect of tunnel size, advance rate, and depth of cover on the stand-up time of tunnels in squeezing ground was investigated through a series of 12 physical model tests. The stand-up time, defined as the time elapsed before instability develops, was found to be characterized by increasing deformations and deformation rates rather than a catastrophic collapse of the tunnel. Test results showed a 25% increase in stand-up time was realized by halving the size of the opening (from 5.0 m dia. to 2.4 m dia. when scaled to prototype dimensions) or by decreasing the advance rate by a factor of four (from 1.3 m/hr to 0.3 m/hr for the 5.0 m dia. tunnel). Depth of cover was described in terms of the ratio of confining pressure to material strength. Decreasing the depth (or increasing material strength) by 10% also increased stand-up time by 25%. In order to establish a predictive capability, a constitutive theory describing the time dependent behavior of soft clays has been developed.

  • Corporate Authors:

    University of California, Berkeley

    Institute of Transportation Studies Library
    Berkeley, CA  United States  94720

    Department of Transportation

    Office of University Research, 1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Myer, L R
    • Brekke, T L
    • Korbin, G E
    • Kavazanjian, E
    • Mitchell, J K
  • Publication Date: 1977-6-30

Media Info

  • Pagination: 208 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00167321
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: DOT-TST-77/59 Final Rpt.
  • Contract Numbers: DOT-OS-50108
  • Files: NTIS, TRIS, USDOT
  • Created Date: Nov 23 1978 12:00AM